Heat shield means are already known for use in all-plastic headlamps having a rectangular construction such as described in U.S. Pat. Nos. 4,280,173 and 4,210,841, both assigned to the assignee of the present invention. In said earlier issued patent, the disclosed heat shield means comprises a metal disc interposed between the lamp filament and the lamp roof. The flat surfaces forming the roof and floor of the truncated reflector are generally parallel to each other and located at the same distance from the lamp optical axis. In the subseqently issued aforementioned patent, the heat shield means is again interposed between the light source filament and the lamp roof by having a substantially planar heat reflecting member suspended from the lamp roof. The function achieved with both type heat shield means is to prevent convection and radiation heating by the lamp filament producing wall temperatures in the region above the filament approaching or exceeding the softening temperature of the plastic.
It would be desirable to provide the same benefit in a lamp construction of this general type but which has too little free space above the lamp filament to accommodate interposition of separate heat shield means. More particularly, the lower profile truncated motor vehicle lamp disclosed in the aforementioned Ser. No. 386,498 application is of such reduced horizontal width that the roof surface of the reflector member is in much closer proximity to the lamp filament so that it is not possible to interpose heat shield means therebetween. While an all-glass construction of said prior art headlamp can eliminate heat distortion problems, it will be appreciated that convection and radiation heating of the roof surface in this headlamp is a far more serious problem than encountered in the prior art all-plastic PAR lamps. Accordingly, an all-plastic headlamp with the configuration disclosed in said aforementioned pending application requires both a relocation of the heat shield means along with a more effective means to prevent heat distortion of the lamp roof.
It is an important object of the present invention, therefore, to provide an all-plastic PAR lamp for vehicle illumination of the low profile rectangular type with effective heat shield means.
It is another important object of the invention to provide heat shield means for all-plastic headlamps of this type which further includes more effective means to remove heat from the interior lamp envelope.
A still further object of the present invention is to provide said heat shield means as an integral part of the reflector roof when molded.